Lubricant



"Ill

Patented Feb. 11, 1941 UNITED STAT-ES LUBRICANT David R. Merrill, Long Beach, Calif., assignor to Union Oil Company oi California, Los Angeles. Calif., a corporation of California No Drawing. Application May 3, 1938. Serial No. 205,737

r, I 27 Claims.

This invention relates to lubricating oils, and particularly applies to mineral lubricating oils adapted for use in severe service internal combustion engines especially those commonly known as Diesel engines and high output aviation engines.

The object of the invention is to provide mineral lubricating oils, which will be highly stable against deterioration, as by oxygen and light, and when in use will overcome sticking of piston rings, valves and the like and the formation of sludges or sludge and lacquer deposits on the engine parts and will be free from corrosive influences upon wrist pin bushings, crank shaft bearings and similar parts of such internal combustion engines.

Compositions suitable for this purpose belong to the class of compounds known as oil-soluble soaps. These oil-soluble soaps exhibit a permanent state of solubility or dispersion in the lubricating oil as distinguished from soaps which tend to cloud or gel or stratify, at least in the proportions in which they are used for the present purposes.

Primarily the present invention resides in the employment in mineral lubricating oils of oilsoluble metal soaps, such as alkaline earth metal soaps or similar soaps, or hydrogenated or partially hydrogenated rosin acids, and also where such soaps are used with sulfur as in lubricating oils naturally containing appreciable sulfur. By the term rosin acids is meant primarily abietic acid which ordinarily predominates in rosin and rosin oil, but the term is intended to include kindred acids such as d-pimaric acid and the sapinic acids which are ordinarily present in rosin and rosin oil in smaller quantities than the abietic acid. This term and suitable equivalents will be explained more fully hereinafter.

- Preliminary In preparing soaps of such hydrogenated abietic or rosin acids, according to this invention, direct neutralization with a neutralizing material, such as calcium hydroxide, may be employed; or esters of the hydroabietio acid, such as the methyl ester, may be employed andthe calcium soap formed therefrom; or hydrogenated rosin or hydrogenated rosin oil may be subjected to saponification as with calcium hydroxide or calcium oxide and filtered and the filtrate employed in its entirety; or sodium soaps of a relatively pure hydroabietic acid or sodium soaps of hydrogenated rosin or hydrogenated rosin oil or other source of rosin acids may be prepared and the calcium or other desired soaps produced therefrom by metathesis. Inasmuch as esters, for'example the methyl ester, of dihydroabietic acid are liquid, these materials are especially convenient of employment, but the invention is not limited thereto.

In employing approximately 1.25% to 1.50%

of calcium soap of such hydrogenated rosin acids, highly eflicient results have been obtained against the sticking of rings and valves and accumulations of resins, varnishes and the like in engine parts, and where sulfur has been incorporated, especially sulfur naturally occurring in the oils as herein indicated, corrosive tendencies by organic acids toward sensitive bearings, such as cadmium silver bearings, wrist pin bushings, and the like have also been overcome.

Referring particularly to calcium soaps of hydrogenated rosin acids, or dihydroabietic acid, as preferred examples, such soaps are to be added to an otherwise satisfactory mineral lubricating oil in amounts ordinarily from about 1% to 2%.

The mineral lubricating oil should in itself possess good solvent power for the soaps and preferably also possess appreciable solvent power for gums, resins, and varnishes which tend to form in heavy duty internal combustion engines or to accumulate in the oil from unburned or partially burned fuel residues, especially as in Diesel engines.

A desirable oil for average purposes is an ordinary California or naphthenic base mineral lubricating oil which in a typical case will have a natural sulfur content of about 0.5%. Where the final oil product is intended to be thoroughly non-corrosive, as where it is to be employed with highly corrosion-sensitive bearings such as cadmium silver bearings, the oil preferably should have a suflicient or further offsetting sulfur content to overcome any corrosive tendencies on the part of the soap such as might be generated in the oil during use as by hydrolysis of the soap or by reason of the presence of some constituent used in or with the soap. Such sulfur content also imparts additional oiliness and extreme pressure characteristics to the product, and it may be that such additional sulfur content exerts antioxidation effects upon the soap, because it has been observed that greater sulfur content (for example 2%) reduces the amount of deposits and produces softer deposits than smaller quantities such as 0.5% of sulfur. Such additional sulfur content may be very desirably obtained by employing a naphthenic base oil having a high natural sulfur content wherein organic sulfur compounds to the extent of a sulfur content of perhaps 3% or 4% on the oil remains after ordinary refining and acid treatment of the lubricating stock. Such high natural sulfur content naphthenic base oils are Santa Maria Valley (California) oils, Smackover (Arkansas) oils, Spindletop (Texas) oils and some Mexican oils. Again such high sulfur content oils may be combined with the above mentioned ordinary California or other naphthenic base lubricating oils to increase the sulfur content of the latter and blended in proportions from as low as 10% to as high as 50% or even approaching 100% of the high sulfur oil so as to yield a total sulfur content of as low as about 1% upwards to 4% or even higher if possible. Increased sulfur content offsets corrosive tendency resulting from the soap or other addition agent, and as a result the oiliness and extreme pressure characteristics will be greater. In addition to blending as indicated to increase the sulfur content, high sulfur content solvent extracts of lubricating oils may be added to 0118 deficient in sulfur. In the use of naphthenic oils of low sulfur content, as for example 0.15% sulfur, the addition of some oil of high natural sulfur content has been found desirable to give a product of enhanced oiliness.

The invention The invention therefore may be briefly stated as also residing in a mineral lubricating oil, particularly a naphthenic base mineral lubricating oil containing oil-soluble hydrogenated rosin acid soaps as typified by soaps of hydrogenated abietic acid, in amount insumcient to impart grease-like characteristics and preferably between about 1% and 2%, or within limits of about 0.5% and 2.5%. The invention resides in the use of such hydrogenated rosin acid soaps whether derived from relatively pure abietic and kindred acids as segregated from rosin materials,

or produced directly from hydrogenated rosin or rosin oils wherein all of the filterable saponlflcation products are employed. The invention resides further in the use of such soaps in a mineral lubricating oil, especially naphthenic base oil, with a sulfur content to increase oilinessand extreme pressure characteristics and overcome possible corrosive tendencies, and especially with such sulfur in amount to overcome corrosion to unusually sensitive bearings such as cadmium silver bearings. W

The invention also resides in the use of lubricating oils containing naturally-occurring sulfur in amounts ranging from less than 1%, but at least from about one-fourth percent or preferably one-half percent up to as high as about 5%. The invention includes also the use of petroleum fractions of high sulfur content which may be added to otherwise satisfactory lubricating oils to provide the desired sulfur content in the product, such fractions being obtained by distillation or solvent extraction or similar treatment of sulfurbearing stocks, and this will include the addition of about 10% to 50% or more of the above mentioned Santa Maria Valley oils to otherwise satisfactory lubricating oils such as the mentioned ordinary California or naphthenic base lubricating oils where their sulfur content is not deemed sufficiently high.

Definitions For purposes of this disclosure dihydroabietic acid (CrsHznCOOI-I) is taken as having the following probable structural formula:

CH: COOH The two hydrogens appearing in parentheses are the two hydrogens addedto the abietic acid (CiIHflCOOH), the remaining double bond presumably having shiftedto the position indicated. Chemists are not clear as'to the exact formula for this compound but the above is believed to be the most probable structure in the light of present chemical knowledge. This formula is here advanced in order to describe in the most clear and full manner the nature of these materials but I do not desire to be limited thereto. The product of this invention, irrespective of its actual chemical composition, which forms the subject is produced as described below.

In employing hydrogenated rosin acids, such materials may be either hydrogenated to the point of saturation (e. g. tetrahydroabietic acid), or especially they may be hydrogenated to eifect a partial saturation of the acid molecule (e. g. dihydroabietic acid), or to yield mixtures of such acids with unhydrogenated rosin acids from which soaps or mixtures of soaps are obtained. With further reference to the terms rosin acids" and "abietic acids, it is intended to include all those rosin materials which contain acids akin to abietic acid and produce the desired hydrogenated soaps of the present invention. As is well known, rosin is the relatively high melting point residue obtained from the distillation of natural crude turpentine from living trees and known as gum rosin, or from the steam distillation or solvent extraction of the wood of pines and furs, such as cured or fatty pine stumps, and known as wood rosin. The turpentine passes 03 under low temperature distillation conditions to form "gum turpentine" when the exudate from the living tree is distilled, and to form "wood turpentine when the products from old or cured wood are distilled. From these rosin residues left after the turpentine has been distilled ofl, normally liquid rosin oils may be distilled out in one or more fractions including redistillation if desired, leaving a still higher melting point gum or wood rosin as the case may be.

The materials from wood distillation correspond generally with those from the living trees but differ in some particulars not clearly understood. However all of these rosin oils and resins contain abietic acids which may be used for the present purposes. Apparently the abietic acids which are distilled over in the rosin oils are of lower molecular weight than the polymers remaining in the rosin bottoms; or the different abietio acids may be isomers of one another. The constitution above given for abietic acids is furnished as merely representative and there are undoubtedly many so-called abietic acids of varying constructions.

It is generally understood that abietic acid as such does not exist in the natural secretions but that other constituents, possibly isomers, are present having about the same composition as abietic acid itself, namely CisHrsCOOH. In any event, heat treatment and also acid treatment yield abietic acid, and it would appear that heavier heat treatment yields various isomers of abietic acid and probably polymers thereof also. These acids, which are commonly referred to as abietic acid and are here generally considered as consisting of abietic acid and its polymers principally but containing also d-pimarlc and sapinic acids, are in general the acids intended when the term rosin acids" is employed, this term including also the various isomers and polymers of these acids and kindred acids present in or obtainable from rosin. Inasmuch as all of these materials apparently are valuable for these purposes, it is, therefore, possible to saponifyhydrogenated rosin or rosin oil and to use the entire product resulting, as well as to use soaps from the relatively pure segregated hydrogenated acids or esters. It is to be understood that where the acids are segregated, they are ordinarily hydrogenated after segregation, and that where rosin and rosin oils are employed, these materials are themselves hydrogenated. After hydrogenation of these materials, the soaps are then prepared. If esters of the hydrogenated acids are the available starting material, these are first hydrolyzed, the acids recovered, and the soaps then produced by neutralization. In preparing such esters the hydrogenation may be effected either before or after esterification.

Operations As to operating procedures, most of these are within the range of knowledge of the ordinary chemist skilled in the art, and inasmuch as much work hasbeen done along these lines, detailed descriptions in some instances are not furnished. Briefly, hydrogenation may be effected in the presence of suitable hydrogenation catalysts such as platinum, and saponification of the hydrogenated acids or the hydrogenated rosin or the hydrogenated rosin oil effected by heatingthe respective materials in the presence of the selected neutralizing material, of which calcium hydroxide as hereinbefore referred to is typical and preferable. Where the mentioned hydrogenated segregated acids or rosin or rosin oils are to be treated for formation of the soaps, such operations may take place under suitable heat conditions to effect liquidity in the presence of lubricating oil such as is to be used in the final product, or in the presence of other diluents, or otherwise as may be preferred or deemed desirable by the operating chemist. Where saponification of hydrogenated rosin and rosin oils with hydrated lime is effected in the presence of lubricating oil or other solvent, the eventual product is filtered for the removal of any solids, and the resultant concentrate is employed for addition to the preferred mineral base oil above described in such proportion as is required to yield the desired soap content in the final oil, namely between about 1% and 2%. Where soaps are to be formed from esters of hydrogenated rosin acids, as are now available on the market in the form of methyl esters under the trade name Hercolyn," the acids may be prepared therefrom as by hydrolysis with caustic alkali under rather severe conditions in the presence of a suitable solvent or diluent such as glycerin, whereby to form, for example, potassium dihydroabietate which is treated with sulfuric acid whereby the dihydroabietic acid is freed and is then taken into solution in a solvent such as petroleum ether. A suitable soap, such as calcium soap, may then be prepared by heat treating the recovered acids in the presence of lubricating oil with hydrated lime at elevated temperature to neutralize the acids, the solids being removed by filtration at an elevated temperature sufliciently high to insure ready filtration.

The various hydrogenating, esterifying and kindred reactions herein indicated may be effected in any known or preferred manner as will be apparent to the skilled chemist. Appropriate operations, especially for some of the less well known reactions, will be found described in the companion Humphrey Patents 1,877,179 and 2,099,066 for Esteriilcatlon with subsequent hydrogenation and for Hydrogenation with subsequent esterification, respectively; Byrkit 1,973,- 865 and 2,094,117 for Rosin hydrogenation; Butts 1,979,671 and 2,042,585 for Hydrogenation of esters; Kaiser 2,074,963 for Esteriflcation; and similar patents. Also, corresponding materials may be bought on the open market.

Substitutes for calcium are preferably magnesium, zinc and aluminum, whose soaps may be employed where sufliciently soluble in the oil to be used. Other bases, where their soaps are sufilciently oil-soluble are sodium, potassium, manganese, tin and the like, and also organic bases such as amyl amine, cyclohexyl amine, morpholine, triethanolamine and the like.

In addition to the soaps here described, it may also be advantageous under many circumstances to add other materials. For instance, chlorinated soaps of other types or other well known chlorine compounds may be employed such as chlorinated paraflln wax, chlorinated naphthalene, chlorinated diphenyl, chlorinated methyl stearate and the like. Again sulfur and/r chlorine may be imparted to the oil by sulfurizing or chlorinating an ester, such as methyl ester, of abietic acid, this agent being introduced for oiliness and/or non-corrosion purposes in addition to the soap. For these purposes about 0.25% to 3% of a sulfurized ester or a chlorinated ester or a sulfochlorinated ester may be used in addition to the 1% to 2% soap of the hydrogenated rosin acid.

In employing special sulfur-bearing oils here disclosed, the mentioned hydrogenated rosin acid soaps may be used in .the Santa Maria Valley, Smackover and Spindletop oils mentioned which have high natural sulfur content; or they may be used in blends of such oils with other suitable naphthenic base oils such as the ordinary naphthenic base oils containing, for example 25% to 50% of high sulfur oil; or I may use such suitable ordinary naphthenic base oils to which have been added petroleum fractions of high sulfur content which may have been produced by distillation, solvent extraction, adsorption on active surfaces such as activated alumina or silica gel and the like, whereby products having a natural sulfur content of sufilcient degree are obtained. Such a sulfur range may be between about 1% or less (such as 0.5%) and about 5% or according to requirements.

Inasmuch as the methyl ester of dihydroabietic acid is commercially available on the open market, such a material has been used as a starting material and the acids recovered by hydrolysis. As a specific example, a product now being produced by the Hercules Powder Company of Delaware is available under the trade name "Hercolyn" which is believed to be chiefly dihydromethyl-abietate. This material presents the following specifications:

Purity 92%-94% ester Refractive index at 20 C 1.517 Specific gravity at 20/20 C 1.032 Acid number 5 Saponiflcation number 24 Color (Lovibond-50 mm. tube)- 5 amber Viscosity at 25 C 27 poise Flash point (Cleveland open cup) 183 C. Flame point (Cleveland open cup) 218 C.

Vapor pressure (mm. Hg.)

25 C Less than 0.01

- 100 C Less than 1.0

200 C 4 250 C 29 300' C 135 Boiling point 365370C.

The following is given as a specific procedure in preparing hydrogenated abietic acid and eventually calcium or other indicated soaps thereof: 2000 grams of said methyl ester of dihydroabietic acid and 600 grams of potassium hydroxide (an leaving a clear solution of potassium dihydroabietate in the glycerin with the excess potassium hydroxide. This mixture is dissolved in about 3 gallons of water and then shaken up or otherwise agitated with about 2 parts of petroleum ether to wash out the unsaponified material, and the petroleum ether solution is removed. To the resultant water solution containing the soaps, an excess of 1:1 or other dilute sulfuric acid is added, whereby the water-insoluble free dihydroabietic acid separates. This free acid is then put into solution. in petroleum ether or similar light solvent, either by separating from the water solution and subsequently dissolving in the solvent, or by adding the petroleum light solvent to the water mixture, agitating thoroughly to effect solution of the dihydroabietic acid in the petroleum ether and, removing the resultant supernatant layer of dihydroabietic acid solution by decantation from the lower layer or water solution containing the sulfuric acid and potassium sulphate. After washing the dihydroabietic acid solution with water, the light solvent is then distilled off at elevated temperature as by means of a slow stream of gas or otherwise. The resultant free dihydroabietic acid is solid at normal temperatures, possesses an acid number between about 155 and 165 and Hanus iodine number which has been found to vary with different samples from 83.5 to as high as 110. The value of 110 in comparison with the theoretical figure of 84 may represent experimental error in the test or may indicate the presence of a limited proportion of unhydrogenated rosin acids.

Such dihydroabietic acid is dissolved in a small quantity of the petroleum lubricating oil to be used in the final product, employing temperatures of around 250 F. to effect solution. The

resultant solution is then added to an additional quantity of the lubricating oil at about F. in quantity sufficient to yield an eventual concentrate of about 7% to 10% soap. To this mixture about 15% to 20% of hydrated lime based on the acid present is added, along with about 0.1% water based on the total and about ,4 diatomaceous earth based on the total, the earth being employed to insure good subsequent filtration of uncombined lime. The temperature of this mixture is then raised to somewhat over 250 F. or up to about 275 F. This temperature preferably is held as high as possible without causing undesired darkening of the product, 275 F. representing the practical desirable limit. The temperature condition is maintained for about three to five hours or long enough to complete neutralization to the desired extent and the formation of calcium dihydroabietate. Upon completion of the saponificatlon operation, the temperature is raisedto about 325 F. to 350 F. and the mass sufiiciently dehydrated to insure against any subsequent tendency to gel. This temperature also insures easy filtration, and the solids are filtered out through a filter precoated with a small quantity of any of the well known diatomaceous earth filter aids or the like, care being taken to avoid the use of filter aids either of character. or in quantity sufficient to effect removal of substantial amounts of the soap from the oil as by adsorption. The filtrate. is then cooled and constitutes an oil-soap concentrate typically of around 7% to 10% soap content which is convenient for subsequent use inasmuch as its viscosity is not too high for convenient blending. The final blends are effected merely by addition, at around F. for example, of appropriate quantities of this concentrate to additional quan- 3 of around 275 F., the operation being continued until the desired extent of saponification is effected. This results in a sort of grease and by reason of the greater concentration, the saponification period is reduced substantially. In order to' obtain from this grease-like mixture a suitable concentrate, additional 011 is added to said mixture while hot and the temperature raised sufliciently to efiect dehydration, for example 325 F. to 350 F. This temperature also aids filtration which may be facilitated by the addition of a small percentage of diatomaceous earth which acts to assist separation of excess lime and to clarify the rosin derivatives. This hot product may be filtered through a precoated filter as above indicated, and the concentration of soap may be as high, if desired, as will permit convenient filtration at the indicated temperature. As an alternative to filtering in either of the-instances above described, it may be possible to centrifuge the materials without the employment of diatomaceous earth or other filter aid.

Similarly, in both instances the presence of an acid number in the final product (as hereinafter stated) tends to make the soap-oil mixture more fluid and correspondingly further facilitate filtration, this function of acid number being in addition to the stated stabilizing or solubilizing function of the free acid for the purpose of insuring soap retention in the presence of moisture, as hereinafter mentioned. All of these indicated concentrates are capable of subsequent dilution to the desired soap content of around 1 to 2% as previously indicated, such blending ordinarily occurring at temperatures of around 125 F. to F. a

- Water content In connection with preparation of these concentrates, the mentioned dehydration, to insure sufiicient'. stability of products, preferably should be such that in a concentrate containing 40% soap the water content should be well under 1%, and a 7% concentrate should be dehydrated to a water content of less than about 0.2%, in order that a final blend, such as one containing 1.33% scan. will have a water content well under 0.05%. Such low water content blends are resistant to gelation and are still further resistant thereto when the final blend has an acid number of at least around 0.45, as discussed below.

Acid content For the preparation of a final blended oil for use in Diesel engines or other severe service internal combustion engines, it is preferable to employ a concentrate prepared as above described containing a calcium dihydroabietate (or similar hydrogenated rosin acidv soap of calcium or the like) possessing an acid number high enough that the final oil product shall have an acid number of at least about 0.45. By acid number is meant the amount of KOH in milligrams necessary to neutralize the acidity in one gram of the compounded product, and here refers to the A. S. T. M. Method B for Compounded Petroleum Products" as distinguished from Method A for Petroleum Products. These methods are found in the A. S. T. M. Standards for 1936, test number Dl88-27T described on pages 629 to 631.

Oils of this invention prepared with acid numbers of at least .4 to .45 according to said Method B appear to be more stable than oils with low acid numbers, and the soaps are retained better in solution in the oil. Also such an acid number assures against the setting up of a gel (as above indicated) oriconsistent emulsion (i. e. emulsion having heavy consistency or exhibiting a yield point) during storage or shipping under such circumstances as may afford the presence of a small quantity of moisture. Thus, higher acid number increases the water tolerance. Ordinarily for Diesel engine and similar uses, an acid number of about 0.4 to 0.5 is preferable.

Such a desirable acid numbermay be obtained either by restricting the quantity of hydrated lime employed in the preparation of soap, or by limiting the heating time to effect the desired degree of saponiflcation, or more conveniently by adding to a concentrate prepared with an excess of lime a suitably calculated quantity of dihydroabietic acid. Obviously the acid number can be suitably adjusted by either of these procedures or any other preferred method, such as the addition of small quantities of hydrogenated rosin or rosin oil.

Where hydrogenated rosin or hydrogenated rosin oil is to be used as the acidic material, this is dissolved in lubricating oil and saponified with hydrated lime in substantially the same manner as above indicated in using the acids recovered from the esters by hydrolysis. In employing such materials all the constituents entering into solution in the 011 along with the soap are retained and constitute a part of the product.

Final oil product A typical final lubricating oil product for use in Diesel engines consists of a base lubricating oil containing 1.33% calcium soap of dihydroabietic acid according to the process herein described. The S. A. E. 30 base oil may consist of about one-third Santa Maria Valley or other high sulfur lubricating oils (naphthenic) heretofore mentioned, and about two-thirds of a typical California or other typical naphthenic base mineral lubricating oil. These base oils may be varied to use from perhaps as little as 10% of the Santa Maria Valley 011 up to about 50% Gravity A. P. I. at

thereof, or even up to 100% high sulfur type oil. The Santa Maria Valley S. A. E. 30 lubricating 011 here employed was prepared by treatment with 60 pounds of 98% H2804 per barrel and possesses the following characteristics:

Santa Maria Valley S. A. E. 30 lubricating oil Gravity A. P. I. at Viscosity index-.. 25

60 F 19.0 Viscosity gravity Color N. P, A 2.4 constant 0.889 Flash C. O. C. F 390 Sulfur by weight Fire point C. O. 0. per cent 3.25

"F 450 Indiana oxidation Viscosity at 100 F. test Saybolt Univer- Hours for 10 sal sec 590 mg. per 10 Viscosity at 210 F. gm. sample 22 saybolt Univer- Hours for 100 sal sec 56 mg. per 10 Acid number gm. sample 40 (Method A) 0.04 Pour point F +15 It is to be noted that this oil contains a sulfur content of about 3.25%.' If a lighter S. A. E. grade is used, the sulfur content will ordinarily be somewhat smaller, for example about 3% and if a heavier S. A. E. grade is used, the sulfur content will be somewhat greater, for example about 3.5%. v

The typical California naphthenic base type S. A. E. 30 oil employed possesses the following characteristics:

Viscosity index- 13 60 F. 20.5 Viscosity gravity Color N. P. A.-- 3 constant 0.877 Flash C. O. C. F.. 380 Sulfur by weight Fire Point O. O. C. per cent 0.5

F 425 Indian-a oxida- Vlscosity at 100 F. tion test Saybolt Univer- Hours for 10 sal sec 571.5 mg. per 10 Viscosity at 210 F. gm. sample 15 .Saybolt Univer- Hours for 100 sal sec 55.3 mg. per 10 Pour point F 5 gm sample- 35 Acid number Ash Nil (Method A) 0.04 Carbon residue 0.10

following table:

Blend with 1.33% Blend" calcium without dihydrosoap abietate Gravity, A. P. I. at 60 F 19. i 19.8 Viscosity, Saybolt Universal:

Seconds at 100 F 689. 8 550 Seconds at 210 F 58. 5 55 Viscosity index 11 15 Viscosity gravity constant. 0. 887 0. 884 Flash, 0. 0. C. F 370 370 Fire, C. O. C. F. 445 445 Pour point, F--- e Color, N. P. A 4% 3% Acid number (mg. KOH/g.). O. 45 04 Sulfated ash, percent-by weight 0. 27 Nil Sulfur by weight 1. 88 1. 88

' By Method B. "By Method A.

In the typical example above employing 1.33% soap it will be noted that sulfated ash content of 0.27 is given as determined by reigni-tion after addition of sulfuric acid. The percentage of ash corresponds with the soap content and may be employed for determination of such soap content.

With respect to the presence of sulfur as herein described, particularly naturally occurring sulfur, the percentage may be varied according to requirements. For example, when employing 1.33% calcium dihydroabietate in the typical Callfornia naphthenic oil above described containing 0.5% sulfur, only a very limited amount of deposit appears in the engine but this deposit is inclined to be hard. By increasing the sulfur content to about 2% by blending with the above described Santa Maria Valley oil, the amount of deposit is reduced and in character it is softer. Thus where only a limited amount of sulfur, for example from to 1%, is required for oil'- setting of tendencies towards corrosion of certain bearings or for oiliness and extreme pressure characteristics, such amount of sulfur will be suflicient if there is no objection to the small amount of hard deposit. However, if it is desired to reduce the amount of deposit and its hardness, or to improve anti-corrosion characteristics, or oiliness or extreme pressure characteristics, then the sulfur content may be increased according to requirements up to the limits of high sulfur content oil.

Oils according to this invention have been tested for film strength and extreme pressure characteristicsby a testing machine recently placed on the market known as the Faville-Le- 'Vally or "Falex lubricating oil testing machine and manufactured by the Faville-Levally Company, South Dearborn, Chicago, Illinois. This machine has been described in papers presented to the Society of Automotive Engineers at their September 1937 meeting in Chicago. It gives a measure of both torque and load. It comprises a rotating spindle disposed on a vertical axis, against the sides of which loaded V-shaped jaws are engaged under the influence of means adapted for gradually increasing the loads. The results are given as pounds per inch torque, the figures given in the iollowing table being the average load at which seizure finally takes place. The two oils indicated are the Santa Maria Valley lubricating oil and the ordinary California naphthenic base lubricating oil containing about 0.5% sulfur herein described.

Load tests on Faville-LeVallu machine Average seizure load in Lubrlcatin oil compounds on Falex posit on machine Percent California s m s na hthen- Maria No soap 1.33% calcium it:( 31:80:] Valley content hydroabletate o a u o 5% sulfur small proportion of materials which have escaped hydrogenation and to that extent dilute the hydrogenated materials. Addition agents as herein employed and necessary for these purposes are such as will increase the base oil viscosity only to an inconsequential extent, for example such as indicated in one of the above tables giving data on blends with and without soap. It is to be understood, of course, that a slight viscosityincrease such as that imparted by the use of 1.33% of calcium dihydroabietate oilers no objection.

Another source of rosin acids is found in tallol or tall oil" which is a pine oil by-product from the wood pulp industry containing rosin acids varying between about 20% and 70% and pine fatty acids varying between about 60% and 20%. This pine oil by-product may be hydrogenated to yield the desired hydrogenated abietic and other rosin type acids present and the desired soaps produced therefrom. Saporiification may be efi'ected in the presence of mineral lubricating oil, or in petroleum or. other light solvent, if desired. The pine fatty acids may be considered generally to have the type of constitution of oleic and kindred unsaturated acids but are nevertheless apparently characteristic. The present invention however is not intended to extend to those specially treated and modified rosin acid products which have high "grease-setting or excessive gelling characteristics and therefore would impart excessive viscosity to liquid mineral lubricating oils intended for uses such as internal engine lubrication here described. Such special materials include a rosin product known as "Hyex as described in the Lister Pat- 3 ent 2,103,204 and British Patent 471,629, and other specially prepared or treated material such as that described in the Brennan et al. Patents 2,042,035 and 2,072,628. On the other hand the materials used in the present invention are predisclosures herein made are not only for the puri pose of indicating the preferred forms of the invention as now understood by applicant but also for indicating that these disclosures are to be taken as illustrative rather than as necessaril limiting.

I claim:

y (to 1. A lubricating oil adapted for severe service internal combustion engines comprising mineral lubricating oil containing between about 0.5%

and 2.5% of an oil-soluble soap of hydrogenated {55 rosin acids.

2. An oil according to claim 1 wherein the oil is predominately a naphthenic base oil.

3. A lubricating oil for Diesel and kindred severe service internal combustion engines comprising a mineral lubricating oil of naphthenic type. containing a stable oil-soluble soap of hydrogenated rosin acids in quantity insufficient to impart grease-like characteristics to the oil and substantially increase the original viscosity of the oil but sumcient to overcome ring sticking and the deposit upon rings and pistons of substantial amounts of gummy, resinous and varnish-like materials.

4. A lubricating oil according to claim 1 wherein the soap is principally calcium dihydroabietate.

5. An oil according to claim 1 wherein the soap is sumcient and is adapted to overcome ring and valve sticking and the deposit of gummy, resinous and varnish-like materials and the quantity 3.

thereof is insufficient to substantially increase the a original viscosity of the base oil.

6. A mineral oil adapted for severe service internal combustion engines comprising mineral lubricating oil and between about 0.5% and-2.5% of a calcium soap of hydrogenated rosin acids.

7. A lubricating 011 according to claim 6 where in the base oil is a naphthenic type oil having good solvent power for the soap.

8. A mineral lubricating oil of naphthenic type containing between about 1% and 2% of calcium soap of hydrogenated abietic acids.

9. A mineral lubricating oil according to claim 8 wherein the calcium soap retains suflicient free acid to impart to the 011 an acid number by A. S. T. M. Method B of at least about 0.4.

10. A mineral lubricating oil according to claim 8 wherein the water content does not exceed about 0.1%. I

11. A mineral lubricating oil of California naphthenic base type containing around 1.25% to 1.50% of oil-soluble metal soap of hydrogenated rosin acids, the product having an acid number of at least about 0.45% and a water content below about 0.1%.

12. An oil according to claim 1 containing at least about 0.5% sulfur.

13. An oil according to claim 1 having a natural sulfur content in the order of about 1% to 5%.

Y 14. A mineral oil according to claim 6 wherein the base oil is a naphthenic type oil containing at least 0.5% sulfur naturally occurring in the cfl.

15. A mineral lubricating oil for severe service internal combustion engines comprising between about 0.5% and 2.5% of an oil-soluble alkaline earth metal soap of hydrogenated rosin acids, mineral oil comprising naphthenic base mineral lubricating oil containing a natural mineral lubricating oil surfur content between about 0.5% and about 5%.

16. A mineral lubricating oil for severe service internal combustion engines-comprising a blend of naphthenic base mineral lubricating oil of low sulfur content and' between about 10% and of a high natural surfur content mineral lubricating oil possessing between about 2.5% and 5% sulfur, and an oil-soluble soap of hydrogenated abietic acids between about 0.5% and 2.5% based on the total mineral oil product.

17. A lubricant for internal combustion engines comprising a naphthenic base mineral lubricating oil of low sulfur content and between about 10% and 75% of mineral lubricating oil naturally having a high sulfur content of between about 2.5% and 5%, and an oil-soluble rosin acid soap between 0.5% and 2.5%.

18. A mineral lubricating oil having non-corrosive characteristics toward alloy bearings highly sensitive to organic acid corrosion, containing high sulfur content petroleum fractions imparting a sulfur content to the oil of between about 1% and about 10%, and oil-soluble soaps of hydrogenated abietic acid in quantity insufflcient to increase substantially the viscosity of the original oil but sufllcient to control the deposition of gummy and varnish-like materials upon the rings and pistons of internal combustion engines.

19. A method for the manufacture of mineral lubricating oil comprising dispersing hydrogenated rosin acids in mineral lubricating oils, incorporating a base adapted to produce oilsoluble rosin acid soaps, heating the mixture at temperatures to effect neutralization and form oil soluble soaps without excessive darkening of the oil and to cause solution of said soaps in the oil, filtering the hot product, and recovering the oil-soap solution.

20. A method for the manufacture of mineral lubricating oils comprising heating an ester of hydrogenated abietic acid with an alkali hydroxide in the presence of glycerin to effect formation of alkali hydrogenated abietate, treating the said alkali abietate with mineral acid to produce hydrogenated abietic acid, dissolving said hydrogenated abietic acid in mineral oil, combining such oil solution with a base adapted to produce an oil-dispersible soap of the hydrogenated abietic acid, heating to efiect neutralization in the presence of the oil, and filtering and recovering the hot product.

21. An 011 according to claim 18 wherein the soap is present in amounts between approximately 0.5% and approximately 2.5%.

22. An oil according to claim 18 wherein the soap is present in amount between about 0.5% and 2.5%.

23. A method according to claim 19 wherein the heating is sufficient to dehydrate the mixture sufficiently to insure retention of the solution and prevent any subsequent tendency to gel.

24. An oil according to claim 3 wherein the soap is present in amount between about 0.5% and 2.5%.

25. A lubricating oil for internal combustion engines comprising a mineral lubricating oil containing a minor proportion of stable oil-soluble soap of hydrogenated rosin acids sufllcient to overcome ring sticking and the deposition upon rings and pistons of substantial amounts of gummy. resinous and varnish-like materials but insufficient to impart grease-like characteristics to the oil.

26. An oil according to claim 25 wherein the soap is chiefly calcium dihydroabietate.

27. A lubricant for internal combustion en gines comprising mineral lubricating oil of low sulfur content and between about 10% and 75% of mineral lubricating oil of sulfur content between about 2.5% and 5%. and oil-soluble soap of rosin acids in quantity sumcient to control the deposition of gummy and varnish-like materials upon rings and pistons of internal combustion engines but insumcient in quantity to increase substantially the viscosity of the original-oil.

DAVID R. MERRILL. 

